Identification and Prioritization of Sub-watersheds to Soil Erosion and Sediment Yield Susceptibility Using RUSLE, Remote Sensing, and GIS (Case Study: Abbay-Awash Basin in Wollo Area, Ethiopia)

The effects of soil erosion are most horrible in developing countries, where agriculturalists are very unable to recover soil fertility using purchased inputs. Evidence on soil loss is vital for encouraging farming productivity and natural resource management. Simulation models are the most active way to predict soil loss processes and their result by using geographic information system and remote sensing. Soil erosion modeling used mathematical equations that require many data measurements as well as physical description of the erosion phenomena. The main goal of this research was to delineate areas that require prior soil conservation measures and to predict the amount of soil loss at the Abbay-Awash basin. The soil loss was assessed by using the Revised Universal Soil Equation (RUSLE) model. The layers were then overlaid and multiplied pixel by pixel, using the RUSLE model and raster calculator-reprocessing tool in Arc GIS 10.1 environment. Annual soil losses range from 0 in the lowlands of the watershed to more than 500 tons ha(-1) year(-1) in much of the steeper slopes on tributaries. Based on the analysis, the amount of soil loss in the Abbay basin from Wollo area is about 3.52 million tons per year from 1.765 million hectares and also in the Awash basin from the Wollo area about 0.58 million tons per year from 0.787 million hectares area. A detailed examination showed that the most pronounced RUSLE factor that worsened soil erosion and caused a high soil loss rate was the slope length (L), steepness (S) factors, and low vegetation cover. Thus, planners should adapt their soil and water conservation measure implementation strategies by devoting in the very urgent part of the watershed first and then progressively to the needed part to prevent the influence of runoff at its start point.